It's not clear they would disagree with that. But if we think prisons are suboptimal, we're more likely to support measures that reduce them. I think this is what is meant by

Abolition makes sense, though, only if we see prisons as a site of injustice in and of themselves.

and

In abolishing prison, we force ourselves to answer the difficult question: How do we provide safety and security for all people?

and

An abolitionist framework makes us consider not only reducing mandatory minimums but eliminating them altogether. An abolitionist framework would call for us to decriminalize possession and sale of drugs. Abolition would end the death penalty and life sentences, and push the maximum number of years that can be served for any offense down to ten years, at most.

With these reforms in place, we as a society would have a huge incentive to rehabilitate those in prison, and we would ensure the incarcerated are capable of socialization when they are released. And without being able to depend on prison as a site of retribution, we would have to find new ways to address things like gender-based violence, sexual assault, and domestic violence. And we could then start making the kinds of investments in alleviating poverty that Gottschalk calls for.

But we can’t do that so long as prison exists as a fail-safe.

In other words, abolishing or severely reducing prisons would force us to come up with other ways to ensure safety, and the author can't imagine one worse than prisons.

For what it's worth, the same author wrote https://www.thenation.com/article/abolish-police-instead-lets-have-full-social-economic-and-political-equality/.,